Buggy code:
private boolean quirkCssBorderCollapseInside ; private boolean quirkCssPositioningOneSideOnly ; private boolean quirkIERepaint ; private boolean quirkIESelectListDomUpdate ; private boolean quirkIESelectPercentWidth ; private boolean quirkIESelectZIndex ; private boolean quirkIETablePercentWidthScrollbarError ; private boolean quirkIETextareaNewlineObliteration ; private boolean quirkMozillaPerformanceLargeDomRemove ; private boolean quirkMozillaTextInputRepaint ; private String remoteAddress ; private int screenColorDepth = - 1 ; private int screenHeight = - 1 ; private int screenWidth = - 1 ; private TimeZone timeZone ; private String utcDSTOffset ; private String utcOffset ; private String hostname ; public int getBrowserHeight ( ) { } public int getBrowserVersionMajor ( ) { } public int getBrowserVersionMinor ( ) { } public int getBrowserWidth ( ) { } public String getNavigatorAppCodeName ( ) { } public String getNavigatorAppName ( ) { } public String getNavigatorAppVersion ( ) { } public String getNavigatorLanguage ( ) { } public String getNavigatorPlatform ( ) { } public String getNavigatorUserAgent ( ) { } public String getRemoteAddress ( ) { } public String getHostname ( ) { } public int getScreenColorDepth ( ) { } public int getScreenHeight ( ) { } public int getScreenWidth ( ) { } public TimeZone getTimeZone ( ) { } public String getUtcDSTOffset ( ) { } public String getUtcOffset ( ) { } public boolean isBrowserInternetExplorer ( ) { } public boolean isBrowserKonqueror ( ) { } public boolean isBrowserMozilla ( ) { } public boolean isBrowserMozillaFirefox ( ) { } public boolean isBrowserOpera ( ) { } public boolean isBrowserSafari ( ) { } public boolean isBrowserChrome ( ) { } public boolean isCookiesEnabled ( ) { } public boolean isJavaEnabled ( ) { } public boolean isProprietaryIECssExpressionsSupported ( ) { } public boolean isProprietaryIEPngAlphaFilterRequired ( ) { } public boolean isQuirkCssBackgroundAttachmentUseFixed ( ) { } public boolean isQuirkCssBorderCollapseFor0Padding ( ) { } public boolean isQuirkCssBorderCollapseInside ( ) { } public boolean isQuirkCssPositioningOneSideOnly ( ) { } public boolean isQuirkIERepaint ( ) { } public boolean isQuirkIESelectListDomUpdate ( ) { } public boolean isQuirkIESelectPercentWidth ( ) { } public boolean isQuirkIESelectZIndex ( ) { } public boolean isQuirkIETablePercentWidthScrollbarError ( ) { } public boolean isQuirkIETextareaNewlineObliteration ( ) { } public boolean isQuirkMozillaPerformanceLargeDomRemove ( ) { } public boolean isQuirkMozillaTextInputRepaint ( ) { } public void setBrowserHeight ( int browserHeight ) { } public void setBrowserInternetExplorer ( boolean browserInternetExplorer ) { } public void setBrowserKonqueror ( boolean browserKonqueror ) { } public void setBrowserMozilla ( boolean browserMozilla ) { } public void setBrowserMozillaFirefox ( boolean browserMozillaFirefox ) { } public void setBrowserOpera ( boolean browserOpera ) { } public void setBrowserSafari ( boolean browserSafari ) { } public void setBrowserChrome ( boolean browserChrome ) { } public void setBrowserVersionMajor ( int browserVersionMajor ) { } public void setBrowserVersionMinor ( int browserVersionMinor ) { } public void setBrowserWidth ( int browserWidth ) { } public void setCookiesEnabled ( boolean cookiesEnabled ) { } public void setJavaEnabled ( boolean navigatorJavaEnabled ) { } public void setNavigatorAppCodeName ( String navigatorAppCodeName ) { } public void setNavigatorAppName ( String navigatorAppName ) { } public void setNavigatorAppVersion ( String navigatorAppVersion ) { } public void setNavigatorLanguage ( String navigatorLanguage ) { } public void setNavigatorPlatform ( String navigatorPlatform ) { } public void setNavigatorUserAgent ( String navigatorUserAgent ) { } public void setProprietaryIECssExpressionsSupported ( boolean proprietaryIECssExpressionsSupported ) { } public void setProprietaryIEPngAlphaFilterRequired ( boolean proprietaryIEPngAlphaFilterRequired ) { } public void setQuirkCssBackgroundAttachmentUseFixed ( boolean quirkCssBackgroundAttachmentUseFixed ) { } public void setQuirkCssBorderCollapseFor0Padding ( boolean quirkCssBorderCollapseFor0Padding ) { } public void setQuirkCssBorderCollapseInside ( boolean quirkCssBorderCollapseInside ) { } public void setQuirkCssPositioningOneSideOnly ( boolean quirkCssPositioningOneSideOnly ) { } public void setQuirkIERepaint ( boolean quirkIERepaint ) { } public void setQuirkIESelectListDomUpdate ( boolean quirkIESelectListDomUpdate ) { } public void setQuirkIESelectPercentWidth ( boolean quirkIESelectPercentWidth ) { } public void setQuirkIESelectZIndex ( boolean quirkIESelectZIndex ) { } public void setQuirkIETablePercentWidthScrollbarError ( boolean quirkIETablePercentWidthScrollbarError ) { } public void setQuirkIETextareaNewlineObliteration ( boolean quirkIETextareaNewlineObliteration ) { } public void setQuirkMozillaPerformanceLargeDomRemove ( boolean quirkMozillaPerformanceLargeDomRemove ) { } public void setQuirkMozillaTextInputRepaint ( boolean quirkMozillaTextInputRepaint ) { } public void setRemoteAddress ( String remoteAddress ) { } public void setHostname ( String hostname ) { } public void setScreenColorDepth ( int screenColorDepth ) { } public void setScreenHeight ( int screenHeight ) { } public void setScreenWidth ( int screenWidth ) { } public void setTimeZone ( TimeZone timeZone ) { } public void setUtcDSTOffset ( String utcDSTOffset ) { } public void setUtcOffset ( String utcOffset ) { } @ Override public String toString ( ) { <START_BUG> StringBuffer b = new StringBuffer ( ) ; <END_BUG> Field [ ] fields = ClientProperties . class . getDeclaredFields ( ) ; for ( int i = 0 ; i < ( fields . length ) ; i ++ ) { Field field = fields [ i ] ; if ( ( ( ( field . getName ( ) . equals ( "serialVersionUID" ) ) == false ) && ( ( field . getName ( ) . startsWith ( "class$" ) ) == false ) ) && ( ( field . getName ( ) . startsWith ( "timeZone" ) ) == false ) ) { field . setAccessible ( true ) ; Object value = null ; try { value = field . get ( this ) ; } catch ( IllegalArgumentException e ) { throw new RuntimeException ( e ) ; } catch ( IllegalAccessException e ) { throw new RuntimeException ( e ) ; } if ( field . getType ( ) . equals ( Integer . TYPE ) ) { if ( ( ( ( Integer ) ( value ) ) . intValue ( ) ) == ( - 1 ) ) { value = null ; } } if ( value != null ) { b . append ( field . getName ( ) ) ; b . append ( "=" ) ; b . append ( value ) ; b . append ( "\n" ) ; } } } return b . toString ( ) ; } }

Fix:
StringBuilder b = new StringBuilder ( ) ;